The present invention relates to an apparatus and a method for the detection of chemical agents, in particular, an apparatus and a method for the detection of chemical agents which are suitable for detecting 2,2′-dichloroethyl sulphide (hereinafter referred to as sulfur mustard) and 2-chlorovinyl-dichloroarsine (hereinafter referred to as lewisite 1) with a mass spectrometer by employing atmospheric pressure chemical ionization (APCI).
In recent years, there has been a desire for an apparatus for detecting chemical agents, for a countermeasure against chemical terrorism including the sarin case. A chemical agent is generally detected by its analysis, and examination by gas chromatography mass spectrometry (GC/MS) is a leading method for the detection. In general, the chemical agent itself is rarely detected in a sample and its presence is proved by detecting a decomposition product capable of remaining easily.
As a prior art regarding another apparatus for analyzing a chemical agent, liquid chromatography mass spectrometry (LC/MS) for the separation and analysis of a volatile or nonvolatile compound is known.
FIG. 14 is a diagram illustrating an outline of the structure of an analyzer according to a prior art, in which the liquid chromatography mass spectrometry is employed. The analyzer according to the prior art is explained below. In FIG. 14, numeral 101 denotes a liquid chromatograph (LC), numeral 102 a connecting tube, numeral 103 an ion source, numeral 104 an electric source for ion source, numerals 105 and 109 signal cords, numeral 106 a mass spectrometry section, numeral 107 a vacuum system, numeral 108 an ion detector, and numeral 110 a data processor.
As shown in FIG. 14, the analyzer according to the prior art, in which the liquid chromatography mass spectrometry is employed, comprises the liquid chromatograph (LC) 101 for separating a sample solution into components, the ion source 103 for producing ions from sample molecules which is controlled by the electric source for ion source 104, the mass spectrometry section 106 for subjecting the produced ions to mass spectrometry which is evacuated by the vacuum system 107, the ion detector 108 for detecting the ions subjected to the mass spectrometry, and the data processor 110 for processing data. The zone comprising the ion source 103, the mass spectrometry section 106 and the ion detector 108 constitutes a mass spectrometry apparatus (MS).
In the above, the sample solution separated into components in the liquid chromatograph (LC) 101 is introduced into the ion source 103 operated at atmospheric pressure, through the connecting tube 102. The ion source 103 is controlled by the electric source for ion source 104 through the signal cord 105 and produces ions from sample molecules in the sample solution. Then, the produced ions are introduced into the mass spectrometry section 106 and subjected to mass spectrometry. The mass spectrometry section 106 has been evacuated by the vacuum system 107. The ions subjected to the mass spectrometry are detected by the ion detector 108. The signals obtained by the detection are sent to the data processor 110 through the signal cord 109 to give analytical data such as a mass spectrum or a chromatogram.
The mass spectrometry apparatus in the analyzer composed as described above requires an interface means between the mass spectrometry apparatus and the liquid chromatograph (LC) 101 because ions have to be treated in a vacuum in the apparatus. That is, LC is an apparatus in which a large volume of water or an organic solvent is treated at atmospheric pressure, while MS is an apparatus in which ions are treated in a high vacuum. Therefore, direct connection of these two apparatus with each other has been considered difficult.
A method called Ion Mobility Spectrometry is mainly a method comprising a combination of the ionization of a sample by means of a radiation source and the measurement of the mobility of ions in an electric field. This method is a leading method for on-the-spot detection, and many products employing this method have been produced in Europe and America. The Ion Mobility Spectrometry method is often adopted for many purposes including military purposes because it permits miniaturization of a detector as compared with GC/MS and LC/MS. However, in Ion Mobility Spectrometry, a sample is not distinguished by mass-to-charge ratio (mass number of ion/valence of ion), so that the display of a detection result is rough. Therefore, it is prescribed that soldiers have to carry a detector in order to wear a protective mask when an alarm is sounded.
As a prior art regarding the Ion Mobility Spectrometry method, there is known, for example, the technique disclosed in U.S. Pat. No. 6,225,623 B1.
The prior arts described above involve the following problems. An electronic ionization (EI) technique tends to decompose a substance to be detected because it applies a high energy to the substance itself. In a detecting apparatus employing GC/MS, ions having a molecular weight higher than that of a substance to be detected are difficult to monitor, so that it is difficult to specify a sample. GC and LC treatments for separating a substance to be detected extend the detection time.
The Ion Mobility Spectrometry method does not makes it possible to specify the kind of a chemical agent and is disadvantageous in that it responds to various compounds, resulting in difficult judgment on a sample to be subjected to detection and a high rate of wrong information. As described above, when the Ion Mobility Spectrometry method is adopted, the sample is difficult to specify and the rate of wrong information is high.
An object of the present invention is to solve such problems in the prior arts and provide an apparatus and a method for the detection of chemical agents which are suitable for detecting sulfur mustard and lewisite 1 and are satisfactory from the viewpoint of the speed of detection of chemical agents, the reduction of the rate of wrong information, the specification of the kinds of the chemical agents, and an unmanned continuous-monitoring apparatus.